Functional Design - Critiques and Limits

Critiques and Limits

Every computer system has parts that cannot be functionally pure because they exist to distribute CPU cycles or other resources to different modules. For example, most systems have an "initialization" section that starts up the modules. Other well-known examples are the interrupt vector table and the main loop.

Some functions inherently have mixed semantics. For example, a function "move the car from the garage" inherently has a side effect of changing the "car position". In some cases, the mixed semantics can extend over a large topological tree or graph of related concepts. In these unusual cases, functional design is not recommended by some authorities. Instead polymorphism, inheritance, or procedural methods may be preferred.